A differential assembly of the type contemplated for the present invention is generally of the design shown in U.S. application No. 2,859,641 (GLEASMAN). This patent is incorporated herein by reference to the extent necessary to provide specific details of the structure of the differential assembly.
This type of differential includes a rotatable gear housing, a pair of drive axles received in bores formed in the sides of the housing, and a differential gear arrangement mounted within a main body portion of the housing for driving the axles. The gear housing body portion includes a flange formed at one end for mounting a ring gear or other means for providing power input to the differential from the drive shaft of the vehicle in a conventional manner. The gear housing is provided with a cap at its other end which may be formed as an integral part of the housing or may be removably secured to the housing.
The gear arrangement which is referred to as a "crossed-axis compound planetary gear complex" includes a pair of helical worm or side gears coupled to each axle end, together with so called transfer gears associated with each of the side gears and in mesh with each other for transferring and dividing torque between the axle ends. The transfer gears are mounted in pairs within slots, or windows, formed in the main body portion of the gear housing, and each transfer gear of a pair rotates on an axis of rotation that is substantially perpendicular to the axis of rotation of the side gears and gear housing.
The transfer gears are in reality combination gears, i.e., the middle portion of each gear constitutes a worm wheel portion while the outer ends of the gear are formed with integral spur gear portions. The gear arrangement is such that, for any given pair of combination gears, the worm wheel portion of a first combination gear meshes with one side gear while the worm wheel portion of a second combination gear meshes with the other side gear, and the spur gear portions of the respective combination gears mesh with each other.
The transfer gears are each mounted to the gear housing body by a pin which fits into a pair of axially aligned bores in the housing. Each pin has been allowed to freely rotate about its axis within these bores. This free rotation can increase wear between the pin and bores which, unless otherwise accomodated, may affect the prolonged performance and durability of the differenetial. Under special circumstances, the pins may be weakened by circumferential score marks developed where the pin under deflection contacts the sharp edges of the housing bores.